The present invention relates to operating in the process control industry. In particular, the present invention relates to electronics board life prediction of microprocessor-based field devices based upon repeated measurements of the current drawn by the electronics board.
Efficient manipulation of a process variable in a controlled process requires that faults, in a field device's components or communication circuits, be identified immediately so that appropriate corrective action or appropriate warnings may be implemented. Verification of a malfunction or error prior to stopping the process and removing a field device from a process loop provides inherent efficiency. Present microprocessor-based transmitters contain complex electrical circuits that sometimes appear to have failed, while actually only a leakage or shunted electrical current has occurred. For example, a circuit leakage current that affects loop current may be reported as a transmitter fault.
U.S. Pat. No. 5,481,200 teaches a field transmitter with built-in test equipment. One aspect of the field transmitter includes deriving the current drawn by the electronics of the transmitter and using the derived current to provide a diagnostic output related to the transmitter electronics. The present invention is an improvement upon the teachings set forth in U.S. Pat. No. 5,481,200. As will be apparent later in the specification, embodiments of the present invention allow earlier detection of problem situations and thereby facilitate more effective corrective action.